Answer:
[tex]\large\boxed{D.\ -12x^2-3x+27}[/tex]
Step-by-step explanation:
[tex]f(x)=-9x^2-7x+12\\\\g(x)=3x^2-4x-15\\\\f(x)-g(x)=(-9x^2-7x+12)-(3x^2-4x-15)\\\\f(x)-g(x)=-9x^2-7x+12-3x^2-(-4x)-(-15)\\\\f(x)-g(x)=-9x^2-7x+12-3x^2+4x+15\\\\\text{combine like terms}\\\\f(x)-g(x)=(-9x^2-3x^2)+(-7x+4x)+(12+15)\\\\f(x)-g(x)=-12x^2-3x+27[/tex]
